Beryllium-free high-strength copper alloys

ABSTRACT

A beryllium-free high-strength copper alloy includes, about 10-30 vol % of L1 2 -(Ni,Cu) 3 (Al,Sn), and substantially excludes cellular discontinuous precipitation around grain boundaries. The alloy may include at least one component selected from the group consisting of: Ag, Cr, Mn, Nb, Ti, and V, and the balance Cu.

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Activities relating to the development of the subject matter of thisinvention were funded at least in part by United States Government,Naval Air Warfare Center Contract No. N68335-07-C-0108, and thus may besubject to license rights and other rights in the United States.

BACKGROUND OF THE INVENTION

Copper-beryllium alloys achieve yield strength above 965 MPa (140 ksi)and are widely used in aerospace bushings. However, the U.S.Occupational Safety and Health Administration is calling for reductionsin beryllium exposure, because its dust, if inhaled, can cause anoften-fatal lung illness. The leading alternative to thecopper-beryllium alloys is a copper-nickel-tin spinodal alloy such asToughMet®, but its yield strength, in the non-cold worked condition, islimited to 724 MPa (105 ksi). Another alternative is aluminum-bronzecasting. The nominal composition of one existing aluminum-bronze alloyis 10.3 Al, 5.0 Ni, 2.8 Fe, and balance Cu, in wt %. However, its yieldstrength, in the as-cast condition, is limited to 431 MPa (63 ksi). Yetanother alternative is manganese-bronze casting. The nominal compositionof one existing manganese-bronze is 24.0 Zn, 6.2 Al, 3.8 Mn, 3.0 Fe, andbalance Cu, in wt %. However, its yield strength, in the as-castcondition, is limited to 414 MPa (60 ksi). Thus, there has developed aneed for beryllium-free high-strength copper alloys, with mechanical andtribological properties competitive to those of copper-beryllium alloys.Additionally, the properties should be achieved without cold working, toenable components requiring intricate machining or heavy cross-sections.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to copper alloys strengthened byintragranular multicomponent intermetallic precipitates based onL1₂-(Ni,Cu)₃(Al,Sn), useful for sliding wear applications, among others.According to some aspects, the alloys substantially exclude cellulardiscontinuous precipitation around grain boundaries. Cellulardiscontinuous precipitation around grain boundaries can affect themechanical properties of the alloy deleteriously (See Findik, Journal ofMaterials Science Letters 1998; 17: 79-83, incorporated by referenceherein).

According to other aspects, the alloys of the subject invention aresuitable for production of large-scale ingots using conventionalprocessing techniques known to persons skilled in the art. For someapplications, the alloys can be centrifugally cast to near-net shapeparts. The alloys can also be produced by processes such as EquaCast(See U.S. Pat. Nos. 4,315,538 & 5,279,353, and U.S. Patent Application2002/0007879, incorporated by reference herein), Osprey spray deposition(See Hermann, Morris, Metallurgical Transactions A 1994; 25: 1403-1412,incorporated by reference herein), Pneumatic Isostatic Forging (See U.S.Pat. No. 5,816,090, incorporated by reference herein), powder metallurgypossibly employing hot isostatic pressing, and other casting techniques.

According to another aspect, a high-strength beryllium-free copper alloyincludes 10-30 vol. % of a multicomponent intermetallic phase based onL1₂-(Ni,Cu)₃(Al,Sn). Cellular discontinuous precipitation around grainboundaries is substantially excluded from the microstructure to promoteductility.

According to another aspect, a high-strength beryllium-free copper alloyincludes, in combination by weight percent, about 19-24% Ni, about3.0-6.5% Sn, about 1.2-1.9% Al, up to about 0.05% B, and may include atleast one component X selected from the group consisting of: Ag, Cr, Mn,Nb, Ti, and V, and the balance Cu. The alloy includes a multicomponentintermetallic Li₂-(Ni,Co,Cu)₃(Al,Sn,X) phase.

According to another aspect, a high-strength copper alloy includes anintermetallic Ni—V phase. The Ni—V phase precipitates directly from themelt and inoculates fine fcc grains. As a result, the grain diameter ofthe alloy as-cast can be below about 100 μm.

According to a further aspect, a heat treatment method is performedusing a beryllium-free copper-based alloy that includes 10-30 vol % of amulticomponent intermetallic phase based on L1₂-(Ni,Cu)₃(Al,Sn). Themethod includes subjecting the alloy to a two-step aging heat treatment,maintaining the first step of aging between 600° C. and the solvustemperature of the L1₂ phase (generally below 800° C.), and the secondstep of aging between 450 and 550° C. Alternatively, the alloy can besubjected to a slow cooling from the solutionizing temperature of around850 to 900° C. to the aging temperature around 450 to 550° C. at coolingrates below about 80° C./minute.

Other features and advantages of the invention will be apparent from thefollowing description taken in conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To allow for a more full understanding of the present invention, it willnow be described by way of example, with reference to the accompanyingdrawings in which:

FIG. 1 is a systems design chart illustratingprocessing—structure—property relationships for one embodiment of thepresent invention;

FIG. 2 is a graph showing the strengthening efficiency of differentprecipitates in fcc Cu-based matrix;

FIG. 3 is a graph comparing the precipitation strengthening of Ni₃Al tothat achieved by Ni₃(Al,Sn) for various embodiments of the invention;

FIGS. 4A and 4B are composition diagrams showing composition windowsaccording to various embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a systems design chart illustratingprocessing—structure—property relationships according to one embodimentof the present invention. The desired performance for the applicationdetermines a set of alloy properties required. The disclosed alloysexhibit microstructural characteristics that can achieve the desiredcombination of properties and can be accessed through the sequentialprocessing steps shown on the left of FIG. 1.

Aspects of the present invention relate to high-strength copper alloys,having a general absence of beryllium, and strengthened bymulticomponent intermetallic precipitates based on L1₂-(Ni,Cu)₃(Al,Sn).A variety of different precipitation strengthening mechanisms arecurrently used in Cu—Ni alloys. FIG. 2 illustrates strengtheningefficiencies of several such precipitates. Precipitation strengtheningwith the intermetallic L1₂-Ni₃Al phase is known in the art, butsubstantial improvement in strengthening efficiency of the L1₂ phase isdesirable to achieve a viable non-toxic substitute for copper-berylliumalloys. Strengthening efficiency refers to the amount of precipitatephase fraction required to achieve a given yield strength. Lowstrengthening efficiency results in requiring a large amount ofprecipitate phase fraction, which in turn becomes hard to suppressduring quenching following the solution treatment (prior to aging).Accordingly, in one embodiment, Cu—Ni alloys are provided that employ amulticomponent intermetallic phase based on L1₂-(Ni,Cu)₃(Al,Sn) whichexhibits a high strengthening efficiency, and the precipitation of thisphase can be suppressed prior to aging. The multicomponent intermetallicphase may include an element taken or selected from the group of Ag, Cr,Mn, Nb, Ti, and V. FIG. 3 is a graph comparing the precipitationstrengthening of Ni₃Al to that achieved by Ni₃(Al,Sn) for variousillustrative embodiments of the invention. In one embodiment, the Cu—Nialloys employ 10-30 vol % of the multicomponent intermetallic phasebased on L1₂-(Ni,Cu)₃(Al,Sn).

To increase the driving force of the L1₂-(Ni,Cu)₃(Al,Sn,X) precipitates,in one embodiment, the mole fraction of nickel is constrained to benearly equal to three times the mole fraction of Al, Sn, and X (X═Ag,Cr, Mn, Nb, Ti, and V) in the alloy. The disclosed alloys can be readilyformed in the solution-treated condition and precipitation-strengthened.Additionally, in some embodiments, the alloy has a general absence ofBe, to assist in achieving low toxicity, such as by limiting the contentof Be to up to about 0.06 wt %.

In one embodiment, the alloy includes 10-30 vol % of a multicomponentintermetallic phase based on L1₂-(Ni,Cu)₃(Al,Sn) phase. Cellulardiscontinuous precipitation around grain boundaries is substantiallyexcluded from the microstructure to promote ductility. In anotherembodiment, the alloy is composed of about 19-24% Ni, about 3.0-6.5% Sn,about 1.2-1.9% Al, up to about 0.05% B, and may include at least onecomponent X selected from the group consisting of: Ag, Cr, Mn, Nb, Ti,and V, where the alloy includes a multicomponent intermetallicL1₂-(Ni,Co,Cu)₃(Al,Sn,X) phase. The alloy may contain up to about 1.0wt. % of each included component X. In a further embodiment, the alloyincludes at least about 10% Ni by weight and an intermetallic Ni—Vphase. The Ni—V phase precipitates directly from the melt and inoculatesfcc grains. As a result, the grain diameter of the alloy as-cast is upto about 100 μm in one embodiment such as 30.0 Ni, 2.0 V, and balanceCu, in wt %, and about 60-100 μm in another embodiment.

Table 1 lists nominal compositions of six prototype alloys, according tovarious embodiments of the invention. Alloys A, B, and C were prototypedby vacuum ingot metallurgy, while alloys D, E, F, and G werecentrifugally cast without vacuum melting. All of the embodiment alloysA-G employ multicomponent intermetallic L1₂-(Ni,Co,Cu)₃(Al,Sn,X)precipitates where X is taken or selected from the group of Ag, Cr, Mn,Nb, Ti, and V. Table 1 also includes measured peak properties after heattreatment for each listed alloy. The measured electrical conductivity(σ)is reported in % IACS (International Annealed Copper Standard).

TABLE 1 YS wt % Cu Al Ni Sn Ag Co Cr Nb Ti V B VHN (ksi) σ A Bal. 1.2 244.0 — — — — — 0.8 0.005 376 133 N/A B Bal. 1.5 19 6.5 1 — — — — — 343 —N/A C Bal. 2.0 20 5.0 — — — — 0.1 — 345-355 129 N/A D Bal. 1.5 19 6.5 —— 0.5 0.2 — — 313-356 133 N/A E Bal. 1.2 24 4.5 — — — — — 0.8 370 6 FBal. 1.9 24 4.5 — 1.0 — 0.5 — — 312-366 N/A G Bal. 1.9 24 3.0 — 1.0 —0.5 — — 294-325 N/A Miki Bal. 3.0 30 — — — — — — — 281 104 N/A ToughBal. — 15 8.0 — — — — — — 110 N/A Met

The prior alloy disclosed by Miki and Amano (Miki, Amano, Mater TransJIM 1979; 20:1-10) contains a large L1₂ phase fraction of 31%, yet showsa limited Vickers Hardness of 281 and an estimated yield strength of 717MPa (104 ksi). However, the alloy embodiments A-G with L1₂ phasefractions below about 30%, show Vickers Hardness approaching, or inexcess of 350, with yield strength of about 896 MPa (130 ksi). The highstrengthening efficiency of these alloys was achieved by modifying theL1₂ phase with small additions of tin. The modifiedL1₂-(Ni,Co,Cu)₃(Al,Sn,X) phase was confirmed with advancedhigh-resolution microstructural characterization techniques such aslocal electrode atom-probe analysis.

Prior references have taught away from the addition of tin to Cu—Nialloys for this purpose, as the addition of tin can promote spinodaldecomposition and precipitation of Ni₃Sn. Likewise, prior referenceshave taught that tin-containing Cu—Ni alloys such as the ToughMetCu—15Ni—8Sn alloy are difficult for homogenization and subsequentforging due to incipient melting. The incipient melting in such alloysis caused by the low-melting D0₃-(Ni,Cu)₃Sn phase that is formed as thefinal solidification product due to microsegregation. However, theinventors have demonstrated that the disclosed alloys, if properlyhomogenized, can substantially dissolve the deleterious D0₃-(Ni,Cu)₃Snphase back into the solid solution. In one embodiment, a multistep heattreatment can be used to achieve homogenization, taking care that thefirst step of the homogenization treatment does not exceed the incipientmelting temperature. Some examples of homogenizing heat treatments aredescribed below and listed in Table 2, with respect to alloy E. Afterhomogenization, alloys processed by ingot metallurgy can be hot-workedby conventional forging techniques, such as press forging or rotaryforging at a temperature of about 775-850° C. It is understood thatthese illustrative heat treatments, or other similar heat treatments,can be used effectively with a variety of tin-containing Cu—Ni alloys.

Prior alloys showed cellular discontinuous precipitation around grainboundaries. For example, the alloy disclosed by Miki and Amano showedsuch deleterious precipitation when aged at 600° C. for 20 minutes. Theinventors have also demonstrated such deleterious precipitation in anexperimental alloy with the nominal composition of 12.0 Ni, 2.0 Al, andbalance Cu, in wt %, aged at 500° C. for 4 hours. However, thisdeleterious precipitation can be substantially excluded in theembodiment alloys disclosed herein. Subsequent to the homogenizationtreatment, the alloy can be subjected to an aging treatment. In oneembodiment, a dual-step aging treatment is used, including a first agingtreatment at a temperature between 600° C. and the solvus temperature ofthe L1₂ phase (generally below 800° C.) for 30-60 minutes, and a secondaging treatment at ˜450-550° C. for 8-16 hours. In one embodiment thefirst aging treatment is performed at ˜700° C. and the second agingtreatment is performed at ˜500° C. The first aging treatmentprecipitates L1₂ particles at the grain boundaries, which effectivelyprevents grain boundary migration during the second aging treatment.This treatment prevents subsequent cellular discontinuous precipitationaround grain boundaries which affects the mechanical propertiesdeleteriously. Alternatively, in one embodiment, the alloy can besubjected to a slow cooling, such as described in U.S. Pat. No.4,016,010 (incorporated by reference herein), from the solutionizingtemperature around 850 to 900° C. to the aging temperature around 450 to550° C. at cooling rates below about 80° C./minute.

FIGS. 4A and 4B are composition diagrams showing illustrativecomposition windows according to various illustrative embodiments of theinvention, defined by calculated processability and microstructuralparameters. The upper bound on Sn is partly defined by the calculatedScheil solidification temperature, to ensure subsequent homogenizationand hot-workability. The lower bounds for Al and Sn are shown for analloy embodiment having an L1₂ phase fraction above about 20%. The upperbounds for Al and Sn are designed to ensure quench suppressibility fromthe homogenization/solution temperature, and are influenced by thesolvus temperature of the L1₂ particles, which can be kept to <800° C.to ensure a hot-working window. It is evident that each of alloyembodiments A-G fall within the composition windows shown in FIGS. 4Aand 4B.

By selecting the concentration of nickel, tin, and aluminum, variousembodiments of the disclosed alloys can be produced having at leastabout 10% by volume L1₂ phase at the aging temperature of 500° C. Inaddition, the embodiment alloy A employs small amounts of boron, whichcan improve the grain-boundary cohesion. The embodiment alloy B employssmall amounts of silver, which can improve the wear resistance, and Ni—Vparticles that precipitate directly from the melt and can refine thegrain size through in-situ fcc grain inoculation. The embodiment alloy Cemploys small amounts of titanium, which can improve the strengtheningefficiency of the L1₂ precipitates. The embodiment alloy D employs smallamounts of niobium, which can refine the grain size with Ni₃Nbprecipitates, and small amounts of chromium, which can augmentstrengthening with Cr precipitates. The embodiment alloy E employs Ni—Vparticles that precipitate directly from the melt and refine the grainsize through in-situ fcc grain inoculation. The in-situ inoculationresults in a fine grain size as cast, for example 60-100 μm in diameter,which in turn can result in a dramatic improvement in fracture behavior.The embodiment alloys F and G employ small amounts of cobalt, which canaugment the strengthening with fcc-Co precipitates. Representativetensile properties of the vanadium-containing alloy embodiment E(Table 1) are shown in Table 2 below. As described above, variouscombinations of homogenization treatments and aging treatments wereconducted using samples of alloy embodiment E, and the specifichomogenization and aging treatments used are identified in Table 2. Eachdata point represents the average of two measurements. As seen fromTable 2, the multistep homogenization treatment improves tensileelongation over single-step short-time homogenization treatments.

TABLE 2 Homogenization Aging UTS 0.2% YS Elongation RA TreatmentTreatment (ksi) (ksi) % % 850° C./1 hr + 700° C./30 min + 142 131 1.04.0 WQ WQ + 500° C./8 hr + WQ 850° C./2 hr + 700° C./30 min + 142 1341.0 3.3 WQ WQ + 500° C./8 hr + WQ 850° C./4 hr + 700° C./30 min + 143133 1.0 2.8 WQ WQ + 500° C./8 hr + WQ 700° C./8 hr + 700° C./30 min +141 133 2.7 3.9 750° C./16 hr + WQ + 800° C./8 hr + 500° C./8 hr + 825°C./16 hr + WQ WQ

Following are examples of the experiments relating to development of thealloy of the invention:

Example 1: Alloy A

A vacuum induction melt of alloy A was prototyped by vacuum ingotmetallurgy. The alloy was subjected to a multi-step homogenizationtreatment with first step at 700° C. for 8 hours, the second step at750° C. for 16 hours, and the third step at 825° C. for 16 hours,followed by a water quench. The alloy was then pancake-forged to ˜60%height reduction at a temperature of 825° C. The alloy was thensubjected to a solutionizing heat treatment at 825° C. for 2 hours,quenched with water, and then subjected to a sub-solvus two-step agingheat treatment with the first step of aging at 700° C. for 30 minutesfollowed by a water quench and the second step of aging at 500° C. for 8hours followed by a water quench. The tensile yield strength of alloy Ain this condition was about 910 to 930 MPa (132 to 134 ksi), which iscomparable to copper-beryllium alloys. Furthermore, alloy A in thiscondition showed an elongation of 3 to 8%, superior to as-cast Cu—Bealloys which show an elongation of only 1% at similar strength levels.

Example 2: Alloy B

A 30-lb vacuum induction melt of alloy B was prototyped by vacuum ingotmetallurgy. The alloy was hot-rolled after melting and homogenization.The alloy was subsequently subjected to a sub-solvus two-step aging heattreatment. The Vickers Hardness Number was measured for various agingconditions, as shown in Table 3 below. A representative result is alsoshown in Table 1.

TABLE 3 First 700° C. Second 30 min None 500° C. 4 hr 343 403 8 hr 451550° C. 4 hr 349 8 hr 316

Example 3: Alloy C

A 30-lb vacuum induction melt of alloy C was prototyped by vacuum ingotmetallurgy. The alloy was hot-rolled after melting and homogenization.The alloy was subjected to a solutionizing heat treatment at 900° C. for1 hour, quenched with water, then subjected to a sub-solvus two-stepaging heat treatment, and quenched with water. The Vickers HardnessNumber was measured for various aging conditions, as shown in Table 4below. Representative results are also shown in Table 1.

TABLE 4 First 750° C. 775° C. 800° C. Second 30 min 60 min 30 min 60 min30 min 60 min 500° C. 8 hr 363 361 361 362 352

The yield strength and ultimate tensile strength (UTS) were alsomeasured for samples of alloy C. For these measurements, the alloy wassubjected to a solutionizing heat treatment at 850-900° C. for 2 hours,quenched with water, then subjected to a sub-solvus two-step aging heattreatment with first step of aging at 650-750° C. for 30 minutesfollowed by a water quench and the second step of aging at 500° C. for4-8 hours followed by a water quench. The yield strength of alloy C wasabout 830 to 890 MPa (120 to 129 ksi) and UTS was about 920 to 985 MPa(133 to 143 ksi), which are comparable to copper-beryllium alloys.

Example 4: Alloy D

Alloy D was centrifugally cast without vacuum melting. The castingweighed about 140 pounds and measured 5 inches in height, 15.25 inchesin outer diameter, and 11.25 inches in inner diameter. The alloy wassubjected to a multi-step homogenization treatment with the first stepat 825° C. for 8 hours followed by the second step at 900° C. for 16hours. The alloy was then subjected to a sub-solvus two-step aging heattreatment. The Vickers Hardness Number was measured for various agingconditions, as shown in Table 5 below. Representative results are alsoshown in Table 1.

TABLE 5 First 600° C. 650° C. 700° C. Second 30 min 60 min 30 min 60 min30 min 60 min 500° C.  8 hr 325 339 324 353 349 336 16 hr 332 331 332358 356 342 550° C.  4 hr 313 325 320 333 333 327  8 hr 316 326 329 336324 331

Example 5: Alloy E

Alloy E was centrifugally cast without vacuum melting. The castingweighed about 140 pounds and measured 5 inches in height, 15.25 inchesin outer diameter, and 11.25 inches in inner diameter. The addition ofvanadium in alloy E promoted the formation of Ni—V particles, which inturn inoculated fcc grains and successfully refined the grain size,resulting in a grain diameter of about 60-100 μm. The alloy wassubjected to a multi-step homogenization treatment with the first stepat 900° C. for 8 hours followed by the second step at 950° C. for 16hours. The alloy was then subjected to a sub-solvus two-step aging heattreatment. The Vickers Hardness Number was measured for various agingconditions, as shown in Table 6 below. A representative result is alsoshown in Table 1.

TABLE 6 First 600° C. 650° C. 700° C. Second 30 min 60 min 30 min 60 min30 min 60 min 500° C.  8 hr 339 327 369 364 370 355 16 hr 372 327 362373 383 368 550° C.  4 hr 347 293 325 339 344 337  8 hr 352 311 329 333321 350

The yield strength and UTS were also measured for samples of alloy E.For these measurements, the alloy was subjected to a multi-stephomogenization treatment with the first step at 700° C. for 8 hours, thesecond step at 750° C. for 16 hours, the third step at 800° C. for 8hours, and the fourth step at 825° C. for 16 hours, followed by a waterquench. The alloy was then subjected to a sub-solvus two-step agingtreatment with the first step of aging at 700° C. for 30 minutesfollowed by a water quench and the second step of aging at 500° C. for 8hours followed by a water quench. The compressive yield strength ofalloy E in this condition was about 920 MPa (133 ksi) and UTS was about970 MPa (141 ksi), which are comparable to copper-beryllium alloys.Furthermore, alloy E in this condition showed an elongation of 2.7%,superior to as-cast Cu—Be alloys which show an elongation of only 1% atsimilar strength levels. The elongation of alloy E is further expectedto improve to about 40% upon an optional cold working.

Example 6: Alloy F

Alloy F was centrifugally cast without vacuum melting. The castingweighed about 162 pounds and measured 10.5 inches in height, 13 inchesin outer diameter, and 9 inches in inner diameter. The alloy wassubjected to a multi-step homogenization treatment with the first stepat 900° C. for 8 hours followed by the second step at 950° C. for 16hours. The alloy was then subjected to a sub-solvus two-step aging heattreatment. The Vickers Hardness Number was measured for various agingconditions, as shown in Table 7 below. Representative results are alsoshown in Table 1.

TABLE 7 First 600° C. 650° C. 700° C. Second 30 min 60 min 30 min 60 min30 min 60 min 500° C.  8 hr 348 334 348 355 366 360 16 hr 353 343 356360 365 364 550° C.  4 hr 312 325 334 341 348 335  8 hr 337 338 346 340350 355

Example 7: Alloy G

Alloy G was centrifugally cast without vacuum melting. The castingweighed about 162 pounds and measured 10.5 inches in height, 13 inchesin outer diameter, and 9 inches in inner diameter. The alloy wassubjected to a multi-step homogenization treatment with the first stepat 900° C. for 8 hours followed by the second step at 950° C. for 16hours. The alloy was then subjected to a sub-solvus two-step aging heattreatment to prevent cellular discontinuous precipitation around grainboundaries. The Vickers Hardness Number was measured for various agingconditions, as shown in Table 8 below. Representative results are alsoshown in Table 1.

TABLE 8 First 600° C. 650° C. 700° C. Second 30 min 60 min 30 min 60 min30 min 60 min 500° C.  8 hr 289 278 298 296 317 325 16 hr 303 288 296295 307 321 550° C.  4 hr 272 261 276 260 265 325  8 hr 285 274 297 289294 302

The various embodiments of Cu—Ni alloys disclosed herein providebenefits and advantages over existing alloys, including existing Cu—Bealloys. For example, the alloys provide high strength, high hardness,good corrosion resistance, good wear resistance, good stability atelevated temperatures, and high electrical and thermal conductivity,while avoiding toxicity problems. Accordingly, the disclosed alloys maybe a possible replacement for load-bearing bushings where high strengthand low coefficient of friction are desirable to maximize wearresistance. Additionally, the disclosed alloys may also be suitable foruse in oil and gas drilling components where a combination of goodcorrosion resistance, high strength, and low coefficient of friction isdesirable, and for elevated temperature applications approaching thefinal tempering temperature, which is higher than the alternative CuBeor CuNiSn alloys. Further, the disclosed alloys may also be consideredfor applications where the inherent electrical or thermal conductivityof copper-based alloys is desirable. Still further, the disclosed alloysmay be considered for non-magnetic spring applications where acombination of high spring resilience and low toxicity is desirable.Other benefits and advantages are readily recognizable to those skilledin the art.

Several alternative embodiments and examples have been described andillustrated herein. A person of ordinary skill in the art wouldappreciate the features of the individual embodiments, and the possiblecombinations and variations of the components. A person of ordinaryskill in the art would further appreciate that any of the embodimentscould be provided in any combination with the other embodimentsdisclosed herein. It is further understood that the invention may be inother specific forms without departing from the spirit or centralcharacteristics thereof. The present examples therefore are to beconsidered in all respects as illustrative and not restrictive, and theinvention is not to be limited to the details given herein. Accordingly,while the specific examples have been illustrated and described,numerous modifications come to mind without significantly departing fromthe spirit of the invention and the scope of protection is only limitedby the scope of the accompanying claims.

What is claimed is:
 1. A copper, nickel, tin and aluminum alloy, saidalloy consisting essentially of: by weight percent about 19-24% nickel(Ni), about 3-6.5% tin (Sn), about 1.2-2.0% aluminum (Al), optionally upto 1% by weight of at least one element (X) selected from the groupconsisting of silver (Ag), chromium (Cr), manganese (Mn), niobium (Nb),titanium (Ti) and vanadium (V), no more than 0.06% beryllium (Be), nomore than 0.05% boron (B) and the balance copper (Cu) said alloycharacterized by a microstructure of about 10 to 30 volume percent ofmulticomponent, intermetallic L1₂ (Ni,Cu)₃(Al,Sn,X) phase precipitateparticles in a face centered cubic (fcc) copper (Cu) matrix phase, saidmatrix phase characterized by grain boundaries, said grain boundariessubstantially excluding cellular discontinuous precipitation around saidgrain boundaries, said alloy further characterized by strengthening bysaid multicomponent, intermetallic phase, precipitate particles.
 2. Thealloy of claim 1, wherein the alloy consists essentially of about 19-24%nickel (Ni), about 3.0-6.5% tin (Sn), about 1.2-1.9% aluminum (Al), upto about 0.05% boron (B), and the balance copper (Cu).